The present invention relates to the configuration of the improved turntable drive unit for transmitting the revolution force to the turntable of a microwave oven.
Conventionally, such a microwave oven containing a turntable transmits the revolution force to it via the coupling assembly shown in FIG. 1. In FIG. 1, reference number 40 indicates the turntable, 41 the bottom plate of the oven unit, 42 the drive motor, 43 the output shaft of the drive motor 42, and 44 the coupling assembly, respectively. The drive motor 42 is installed to the motor base plate 45 which is secured to the underside of the bottom plate 41 with screws. A hole is provided on the oven bottom plate 41, while the output shaft 43 is provided in the center of the hole in the direction opposite from the bottom plate 41. The top of coupling assembly 44 is engaged with the bottom of the turntable 40. The coupling assembly 44 is inserted into the hole so that it can be held at its lower shaft using the coupling receiver 46 and the coupling spacer 47 and also via the bearing spacer 48 in order that it can rotate freely. The shaft portion of the coupling assembly 44 and the output shaft 43 are respectively engaged with each other via pin 49 that connects them together, thus making it possible to transmit the revolution force of the output shaft 43 to the turntable via the coupling assembly 44. A rubber cap 50 is provided at the tip portion of pin 49 which is in contact with the shaft portion of the coupling assembly 44 in order that pin 49 can be protected from damage during operation. The coupling receiver 46 is formed by the sheeting process and provides a choke hole 52 which allows rotation of the output shaft 43 to be transmitted to turntable 40. Packing 51 is secured to the outer circumference of the flange of the coupling receiver 46 which is fastened to the bottom plate 41 of the oven.
As mentioned above, since any conventional microwave ovens using the turntable use a number of coupling parts including the coupling 44, coupling receiver 46, coupling spacer 47, and the shaft spacer 48, etc., the production and assembly cost unavoidably rises. In particular, since the conventional turntable has a construction in which the output shaft 43 and the shaft of the coupling assembly is engaged with each other via pin 49, if the turntable 40 is manually rotated while the motor remains off, the revolving force will be directly transmitted to the output shaft 43, thus causing the motor 42 to be destroyed unexpectedly.